Fingerprints of glacial cycles in a non-migratory fish—diversity, structure and evolutionary history of Cobitis elongata

Abstract

The Balkan loach (Cobitis elongata) is different from most loach species in Central and Northern Europe in two important features: It inhabits a single river basin and no asexual reproduction modes nor hybrid biotypes have been recorded inside this species, even though its syntopic occurrence with C. elongatoides has been recorded. It inhabits river stretches with slow flowing water and small particle sediment and feeds by filtering small invertebrates from water. In order to investigate population genetic structure and evolutionary history of C. elongata, we have analyzed samples from its whole distribution range and based our analyses on gene for cytochrome b. Although origin of C. elongata can be dated back to the Miocene epoch, intraspecific divergences occurred during Pleistocene. Phylogenetic reconstruction revealed presence of four genetically distinct units. Star-like shapes of most units in the phylogenetic network, as well as estimation of divergence times, corroborate colonization of wider areas from a single refugium. Although this species is recently tightly attached to its habitats and with very low migration potential, during Pleistocene exchange of favorable and unfavorable periods, it seems that it was able to undertake long-distance migrations and colonize wider areas.